Cerebrospinal fluid immunoglobulins in neurosyphilis.

Using the fluorescent treponemal antibody-absorption (FTA-ABS) test and the solid phase haemadsorption assay (SPHA) Treponema pallidum-specific IgA was found in the cerebrospinal fluid (CSF) of patients with neurosyphilis but not in those with late latent syphilis. The presence of T pallidum-specific IgA in the CSF may inhibit the antitreponemal activity of IgG and thus play some part in the pathogenesis of neurosyphilis.